1. Field of the Invention
Embodiments of the present invention relate to mass spectrometry. More particularly embodiments of the present invention relate to using coded mass spectrometers to reduce the inherent trade off of resolution and sensitivity.
2. Background Information
Mass spectrometers generally operate by ionizing a sample, such as a gas analyte. The ionized sample is generally filtered and the ions are transported by electromotive forces toward a mass detector. The detector detects the ions according to their mass-to-charge ratio through a variety of methods. Thus, the functional elements of a mass spectrometer generally include ionization, mass separation, and ion detection.
FIG. 1 is a schematic diagram of an exemplary conventional mass spectrometer 100. A gas analyte sample 102 is introduced to an ionization chamber 104 between an emitter 106 and an extraction grid 108. Ions are created through an ionization process in ionization chamber 104. During the ionization process an electron may be removed from or added to gas analyte molecules. A portion of the molecules introduced into the ionization chamber are ionized. These ions have a distribution of velocities and directions, and are electromagnetically pulled through extraction grid 108 by operation of negatively biased emitter 106 and a positively charge focus grid 110. A portion of these ions then pass through negatively biased acceleration grids 112. Enough energy is added by acceleration grids 112 that the ions that exit the grid are collimated, as well as relatively homogeneous in momentum and direction. These ions are then filtered through a slit to ensure that the remaining ions have originated from a single line in space. The width of the slit, among other parameters, determines the resolution and sensitivity of the spectrometer. The thinner the slit, the better the resolution but the poorer the sensitivity.
As the ions move through the magnetic field, they are deflected based upon their mass/charge ratio. Higher masses yield a lower deflection for a given charge. the ions strike a position sensitive detector 114. Detector 114 accumalates ion strike positions. This is read out as a function of position, resulting in a mass spectrum. An exemplary mass spectrum 200 is illustrated graphically in FIG. 2.